IN-SITU OBSERVATION OF CRACK TIP DEFORMATION IN A DUPLEX STAINLESS STEEL

The development of dislocation structures in the plastic zone ahead of a crack tip has been in- vestigated in a duplex stainless steel during in-situ deformation experiments in a scanning transmission electron microscope.It was found that the dislocation distribution was significantly different in the ferrite and in the austenite.In the ferrite grains,the dislocations emitted by the crack tip may cross-slip out of the original slip planes and form a broad plastic zone.However,in the austenite,the dislocation free zone is small and the dislocations emitted by the crack pile up in its slip plane.The selection of slip systems at the crack tip depends on the crack tip Schmid factors in both phases.But after large deformation,the selection of the second slip systems at the craek tip in austenite does not depend on the Schmid factors.

850℃时效处理对2205双相不锈钢组织与力学性能的影响

本文研究了在850℃时效不同时间对2205双相不锈钢组织及力学性能的影响,并对其断口进行分析。结果表明:经850℃时效后σ相首先在δ/γ相界和晶界处析出,并随时效时间延长,σ相不断向铁素体方向长大并且含量不断增加。σ相的含量与抗拉强度、延伸率以及冲击韧性存在一定的线性关系。断口形貌由时效初期的韧窝为主,到时效60min后解理+韧窝型断口,到240min几乎完全解理断裂,表明材料的韧性明显降低。